Gaseous electric discharge device



Aug. 7, 1934.

M. PIRANI ET AL GASEOUS ELECTRIC DISCHARGE DEVICE Original Filed Jan. 22. 1951 INVENTORS 2 a: (W! I ATTORNEY Patented Aug. 7, 1934 inseam v oasaops arse-rare nrscnsaan huvrcn ll larcello lt'irani, lBerlin-Wilmersdorl, Martin llteger, Berlin,

and (Georg Gaidies, her-lin Paiulrow, Germany, assignors to General Electric Company, a corporation as New il'orlr (Original application January 22, llliil, denial Non Divided and time application April 2t),

H932, Serial No, lidlhd liio lln Germany, liehruaw ll, 193i! 3 @lainrsn (@l. 176 122) The present invention relates to gaseous elec tric discharge devices generally and more par ticularly the invention relates to such devices in which the gaseous content is a metal vapor, or

in which a metal vapor is a component or the gaseous content.

it is well lrnown in the art that a gaseous electric discharge device having a filling of cadmium rnetal vapor emits a pleasing greenish lolue light;

m however, it is also well lrnown in the art that such cadmium vapor rllleol electric discharge de vices have hitherto been of slight practical use hecause the cadmium vapor condenses readily at temperatures alcove the melting temperatures of 115 the usual" glasses used in the containers or such devices, and further the glass container of such devices hecomes coated with a brown or hlaclr coating alter a short period oi operation of the device to change the color or the cadmium vapor 2Q discharge.

it is the object of this invention to produce a glass suitable for use in the arts generally and particularly as the container ior'cadrniurn vapor hlled electric discharge devices. We have discovered that such a glass having the desired characteristics of being easily workable, highly heat resisting, and chemically stable in the presence of an allrali metal vapor such as a cadmium vapor a ll g for example, may he produced it a hero-silicate glass containing besides the usual 35 glass horic acid, allralies, and alkali earths also cont at least aluminum oxide (AlzOa) and less than 60% silicic acid (S102), where the proportions are given in percentages by weight. A

container made in accordance with the ahove lormula does not become noticeably lorowned or lolackened after 1,000 hours of operation as we have proven Toy experiment.

- it suitable glass is produced if the constituents so are mixed in. percentages by weight according to the following formula:-

Per cent lhorlc orride (B203) 40 to 60 Sodium oxide (NarOL; dto 5 5 Calcl oxide (Ca0) 1012011 Alina A1203) 11 to 13 Silica ($102)..." to

h particrflarly good glass of the above type for the containers of electric discharge devices having allrali metal vapor fillings is a glass having the following composition in percentages by weightz Per cent Eoric oxide (B203) 50 Sodium oxide (No.20) Calcium ovide (CaO) ll Alumina (M2103) l3 Silica (SiOz) 22 It is possible to reduce the alkali and alkali earth content oi the horic acid part or the glass slightly and to replace these by additional amounts oi aluminum oxide and silicic acid in accordance with the following formula:-

' I Per cent idoric oxide (E203) 8.5 to la Sodium oxide and potassium oxide (NazO-l-Kz0) izto 2 Calcium oxide andmagnesium oxide (Ca0+MgO) u 13 to 15 Alumina (A1203) 19 to 25 Silica (S102) to to 00 A particularly good glass of the alcove type for the containers of electric discharge devices havtill ing alkali metal vapor fillings is a glass having the following composition in percentages by weight:-

Per cent Boric oxide (B203) lo Sodium oxide and potassium oxide (Nam-l- K20) Calcium oxide and magnesi 1 oxide (Gaol Mao) l5 Alumina (A1203) 23 Silica (S1102)- id embodiment of a gaseous electric discharge deion vice in which the new and novel bore-silicate glass is used, and

Fig. 2 is a sectional side elevation view of an= other embodiment of an electric discharge device in which the new and novel bore-silicate glass is used.

Referring to Fig. 1 the device comprises a container having a double wall 3, e electrodes 5, d sealed therein and a filling of cadmium vapor, or a mixture of cadmium vapor and discharge con= ducting gas in said container 3, 4. The outer Wall 3 of said container 3, 4 is made of the usual glass, such'as Thiiringer glass, made by the Jenaer Glasswerke Schott and Gen. located in Germany, which possesses a better acid lye and water stability than the boro-silicate glass of this invention, and is not a'fiected by the outside atmosphere as is the boro-silicate glass of the present invention which is slightly hygroscopic. The inner wall 4 consists of the heat resisting, chemically inert with respect to cadmium vapor, borosilicate glass heretofore disclosed. In this form of container the hero-silicate glass wall 4 is protected from the outside atmosphere and further, heat radiation from said wall l is reduced so that the possibility of harmful condensation of the cadmium vapor is lessened. The Thiiringer glass and the boro-silicate glass of this invention have approximately the same coefficients of expansion so that they may be fused together as shown in the drawing.

Referring to Fig. 2 the device comprises a single walled container having electrodes 5, 6 sealed in at both ends thereof, a filling of cadmium vapor, or a mixture of cadmium vapor and. a discharge conducting gas therein, said container being made of two layers '7, 8 inner layer '7 being of the boro-silicate glass of the present invention and outer layer 8 being of the usual weather resisting glass discussed in connection with Fig. 1. If desired, inner glass layer '1 may be very thin.

In both embodiments illustrated in Figs. 1 and 2 the outside walls may contain any desired color filter or they may be of heat absorbing glass as Schottshen glasses BG 9 and 10 which absorb the heat radiating from the electric discharge and are raised to a high temperature to prevent condensation of the cadmium vapor and a consequent loss of vapor pressure even with an extremely cold outside temperature. The BC: 9 and BG 10 glasses above referred to are listed in Bulletin #4213 of the Jenaer Glasswerke Schott and Gen., the title of the bulletin being Jenaer Color and Filter Glass for Scientific and Technical Uses, published in April, 1929. BG 19 glass has the following composition:

Percent Silicic anhydride (S102) 66.12 Boracic acid (B203) 3.69 Aluminum oxide (A1203) 4.99 Ferric oxide (FezOa) 9.13 Ferrous oxide (FeO) 1.99 Soda (NazO) 9.95% m 24 Potassium monoxide (Kz0) 9.29 Zinc oxide (ZnO) 14.69

The'Thiiringer glass above referred to is the usual soda-dime glass having a coefficient of thermal expansion permitting hermetic sealing to a platinum lead wire and well known to the glass trade and the electric lamp art.

While we have shown and described the con tainer of Fig. l as a double wall container, and of Fig. 2 as a single wall container having two layers of glass having different compositions, it will be understood that we contemplate the use of our new and novel boro-silicate glass in electric discharge devices having containers of different structures. For example, the container may be in efiect a double container with no point of fusion between the inner and outer container, in which case a glass having a. greatly different coefficient of expansion than that of the boro-silicate glass of this invention may be used as the outer container and the current leads may have different coeiiicients of expansion over their length to correspond approximately to that of the glass containers at the sealing-in points of said wires in said containers in a manner well known in the art.

This application is a division of our co-pending application, Serial Number 510,222, filed January 22, 1931.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmosphere therein comprising alkali metal vapor, said container comprising a. glass containing alkalies, alkali earths, boric acid, at least 10% aluminum oxide (A1203) and not less than about 20% nor more than 60% silicic acid (SiOz).

2. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmosphere therein comprising cadmium vapor, said container comprising a glass containing between Percent Boric oxide (B203) 40 to 60 Sodium oxide (NazO) 4 to 5 Calcium oxide (CaO) 10 to 11 Alumina (A1203) 11 to 13 Silica (SiOz) 20 to 30 3. An electric discharge device comprising a container, electrodes sealed therein, a gaseous atmosphere therein comprising cadmium vapor, said container comprising a glass containing between Percent lBoric oxide (B203) 8.5 to 15 Sodium oxide and potassium oxide (Na20+K20) 1.2 to 2 Calcium oxide and magnesium oxide (Ca0+Mg0) 13 to 1.5 Alumina (A1203) 19 to 23 Silica (SiOz) 40 to 6G MARCELLO PIRANI. MAR'I'IN REGER. GEORG GAIDIES. 

